In the US, the tap handle threads are 3/8"-16. I believe the taps sold overseas are a different thread (diameter and count). If possible, take one to the hardware store and find a nut that will work on it. You now know the thread size/count you need for inserts. IF it is 3/8"-16, I have some of the brass ones that are 'spares'. If they're a different thread, then you could just get the nuts that match and get them either ground round, or put on a lathe and turned. Use some good glue (two part epoxy would be my choice) and glue them into what you want to use.

That's the problem, I took one to the shop but couldn't find anything that fit, as they. Are perlick525's ordered from the US!

Then you need the 3/8"-16 threaded items... How many do you need? If you can order from online US vendors, might be easier to just do that. If not, there's a couple of us that posted as having spares. Depending on how many you need that is. I'd want the cost of shipping sent to me for this, so that I'm not going into the negatives.